The invention relates to the adjustment of the power of gas-operated apparatuses comprising a first chamber of a first volume containing means for igniting and generating a flame in a combustible gas, a second chamber of a second volume, and means for placing the two chambers in communication, these means being designed to allow the flame to pass.
The invention relates more particularly to the adjustment of the power of internal combustion gas-operated sealing apparatus in which a piston is propelled under the action of the exploding of a mixture of gas and air in order, via its rod, to strike a nail; this is then a gas-operated nail gun, or some other fastening device.
Apparatuses with two chambers have advantages. With two chambers, the first is a precompression chamber which allows the explosion pressure in the second chamber to be increased, the explosion pressure in a volume being proportional to the pressure of the mixture before the explosion. What happens is that, because of the explosion in the first chamber, the combustion pressure thus generated in this first chamber compresses the unburnt mixture which is pushed by the flame front and passes into the second chamber to increase the pressure therein before the explosion occurs in this second chamber. If this second chamber is partially delimited by a drive piston, then by virtue of this precompression, the piston has moved only very slightly forwards at the time when the explosion occurs in this second chamber for propelling the piston, this allowing the piston to derive correct benefit from the energy of combustion of the gas.
When, in addition, there is a fan in the flame-generating chamber, the rate of combustion and the maximum pressure level in this chamber are increased, making it possible to reduce the rise time of this pressure and therefore to further limit the movement of the piston in its drive chamber before the explosion takes place, and therefore making it possible to further increase the power of the apparatus.
It will be noted that the effect of an accelerating fan is more than significant; it allows the pressure rise time to be reduced by a factor of the order of 10.
Being thus in possession of powerful apparatus, the applicant company realized that it could prove beneficial for an operator to have available to him, in one and the same apparatus, a given maximum power which is able however to operate at various power levels below that of maximum power, and this is what the applicant proposes in its invention.